Feeding abrasives to grinding machines



Mingo E359 H929@ p CRUWLEW 3972425@ FEEDING BRASIVES TO GRINDING MACHINES Filed Aug.27, 1923 4 Sheets-Shaw l W @MW/RM@ mm W Aff-*V MW im W29 J. um. cwwhm Lmw FEEDING ABRASIVES TO GRINDING MACHINES Filed Aug.27, 1925 4G .Sheets-Sheet 2 F'EEDING ABRASIVES TO GRINDING MACHINES Filed Aug. 27, 1925 41; Shee'bS-Sheei 3 im@ 13,111929. J. IP. CROWLEY 1,724,259

FEEDING ABRASIVES TO GRINDING MACHINES Filed Aug. 27, 1925 4 Sheets-Sheet. :4

Patented Aug. 13, 1929.

UNITED STATES 1,724,259 PATENT OFFICE.

JOSEPH 1. CROWLEY, OF TOLEDO, OHIO, ASSIGNOR TO THE LIBBEY-OWENS SHEET GLASS COMPANY, 0F TOLEDO, OHIOAGORPORATION 0F OHIO.

FEEDING ABRASIVES TO GRINDING MACHINES.

Application filed August 27, 1923. Serial No.659,436.

rlhis invention relates to an improved process .and apparatus for automatically supplying finely divided vabrasive material, such as sand, mixed in water, to a plurality of plate glass grinding machines. The invention is notlimited for use with any one type of grinding" apparatus, but is particularly designed and adapted lfor use with the grinding machine disclosed in my copending application 633,961, filed April 23, '1923.

According to the present invention, a supply of each of the several grades of abrasive mixture is maintained in au endless pipe circuit. Parallel stretches ofleach of the several pipe lines extend past, and adjacent to, each grinding unit, and mechanism is provided to automatically feed a portion of the supply from any one oi the pipes to each ,machine For example, when the grinding operation of a machine is started a portion of the heaviest grade of abrasive is forced from its pipe line to the machine. After a suitable interval this grade is shut ott and the next finer grade is fed to the machine, and so on until the grinding operation is completed, at which time the finest grade, then being used, is shut ott". A continuous pressure is maintained on the abrasive supply in each pipe-line, which alternately forces portions of the material to such of the grinding machines as are usingthat particular grade of abrasive at the time, or forces a flowV of the material through the pipe-circuit to replenish the -supply of abrasive and keep the solid material in suspension. The used abrasive and water from the several machines flow to 'a common sump from which the better part ot the mixture is pumped to a series of grading tanks. Here it is divided by a settling process 'nto Ithe several grades .of abrasive and dral ed into the storage reservoirs from which the pipe lines are fed, and back into which unused abrasive is discharged.

The invention willbe better understood from the following detailed description of one approved form of the apparatus.

In the accompanying drawings:

Fig. 1 is a plan view of the entire abra sive' supplying system.

F1g. 2 is an enlarged elevation of one of the grinding units and the adjacent'portions of the abrasive feeding system.

Figi 3 is an elevation of the grading tanks, the abrasive reservoirs, and the adjathrough a portion 'of the series of grading tanks. Y

Fig. 6 is a plan View of one of the distributing units for selectively feeding the different grades of abrasive to ,one of the grinding machines.

Fig. 7 is an elevation, partly in vertical section, of the distributing system. A

Fig. 8 is a wiring diagram showing in elevation the timing dials and switches -for automatically controlling the abrasive distributor.

Fig. 9 is an elevation, on an enlarged scale, of one of the gate-valves for intermittently4 interrupting the flow of abrasive through. the pipe-line, and the operating cam for this valve. Y

Fig. 10 is an elevation, taken at rightangles to Fig. 9, and on a smaller scale,

trated is substantially the same as that shown and described in. detail in my prior application 633,961, referred to above. The glass sheet lis freely supported in a shallow recess in the upper face of a rotary table 2. The grinding tool or head 3 rests freely upon the upper surface of the sheet, and the abrasive mixture f1: is fed to the-upper surface of the sheet, and between the sheet and the grinding tool, from the spout 5 at the lower end of the vertical supply pipe 6. The water s and used abrasive which are thrown from the revolving table are caught by the enclosing frame 7 of the machine and the vertically movable door or closure S. and run down through the inclined drain 9 into pipe 10 beneath the machine. The several grades of abrasive, here shown as three, although an desired number might be used by ma ing obvious changes in the mechanism hereinafter described, are maintained in the three parallel pipe-lines 11,

12 and 13, extending` past the several grindtrated three suitable grades of sand serve as a very satisfactory abrasive althoughvother forms of abrasive mixture might be used. The pipe-line 11 contains the heaviest or coarsest grade of abrasive suitably suspended in water. Pipe-line 12 carries 'the intermediate grade of abrasive and pipe 13 the finest grade.

As shown in Fig. 1, the several grinding units, any number of which may be used with this system, are arranged in two parallel rows, the machines facing one another along an intermediate passage. The three parallel pipe-lines or conduits 1l, 12 and 13, are arranged overhead along the center of this passage. Opposite each machine a series of valves or outlets 14, 15 and 16 are' placed in the lower portions of pipes'll, 12, and 13, respectively. Beneath the several outlets 14, 15 and 16 is supported a catch-basin or funnel 17 from which the yabrasive ilows through inclined pipe 18 to the vertical feed pipe 6 of this particular machine.

Each -of the valves 14, 15 and 16 is here shown as of the ordinary rotary stop-cock type, the rotary member 19 having a passage 190 which-lines up with the outlet passage through the valve when in open position, as shown in valve 16, Fig. 7, and which is swung to one side when the valve is closed, as

' shown in'valve 15. Valve 14 in Fig. 7 is shown in elevation. This valve is also in closed position. The lever or crank-arm 191, secured to one end of rotary member 19, has a forked outer end which engages a pin 192 on-an arm 193, adjustabiy secured between nuts 194, on the threaded end 20 of push-rod 21. A pin 23 on push-rod 21 travels in a slot 24 in the vertical bearing 240 for the pushrod. This pin and slot connection limits the vertical movement of the push-rod and its operating connections, and also prevents rotary movement of the rod in its supporting bearing. Rod 21 is normally held in its extreme upper position, with the valve closed, by a spr1ng 25 surrounding the upper p0rtion ofthe rod, and confined between the `head 26 of 'the rod and the supporting frame 27. Frame 27 which supports all ofthe valve operating mechanismuheretofore and hereinafter described, is supported upon the three pipe-linesl or conduits 11, 12 and 13, by means of the clamp yokes 28. Whenone of lthe push-rods is depressed by pushing down upon the head 26, against the action of spring 25, the rotary valve member 19 will be swung to open posltion, as at the right of Fig. 7. In this way an unobstructed passage is 'left in the valve through which a` portion of the abrasive mixture in the pipelinev may be forced as hereinafter described. This abrasive mixture is caught by the basin or funnel 17, from which it flows through pipes 18 and 6 to the grinding table. -When the pressure on head 26 of rod 21 is released,

spring 25 will expand and ,return the parts to their initial position, the rotary valve member 19 being swung back, as shown in valve 15, to positively cut oil the passage through the valve. By shifting the nuts 194 the operating arm 193 may be adjusted vcrti'eally on the threaded lower end 20 of pushrod 21. In this way, the arc of travel of the rotary valve member 19 may be shifted, so that when in open position, the passage 190 through the valve may be partially closed to limit the amount of abrasive allowed to pass through the valve.

Mounted above the several heads 26, in bearings 28 on frame 27, is a horizontal rotary shaft 29, carrying a` series of three cams 30, 31 and 32, which operate respectively the three valves 14, 15 and 16. There is an angle of 90o between cams 30 and 31 and between cams 31 and 32, and an angle of 180 between cams 32 and 30. Cam shaft 29 is rotated at desired intervals by a small electric motor 33 through the train of reducing gears 34, 35, 36 and 37. 37 is a worm wheel iXed near one end of cam shaft 29. Mechanism hereinafter described is adapted to energize motor 33 for a length of time su'ilicient to rotate cam shaft 29 through an angle of 90, after which interval motor 33 is de-energized and the cam shaft stopped.

A control dial 38 is mounted in a convenient position in front of the grinding unit and a rotary control arm 39 is pivoted centrally in 'the face of this dial. Arm 39 is rotated very slowly, while the grinding machine is in operation, through suitable redliction gearing from a small electric motor 40. The dial 38 carries a fixed starting pin 41 and an adjustable stopping pin 42 with which suitable contacts on the rotary arm 39 are adapted to make connection when the arm 39 arrives over or adjacent the respective pins- All of this control mechanism is described and shown in detail in my prior application 633,961, referred to above. When the plate of glass has been placed on the grinding :table and the machine is to be started, arm 39 is manually turned counterclockwise until connection is made with lthe starting pin 41.

Lead 43 from the positive main (see Fig. 8), connects with a. slip-ring 44 about the axis of arm 39.v A suitable brush on this arm makes constant contact with the ring 44. Lead 45 connects with the starting pin 41, lixed in dial 38, and lead 46 connects with Contact ring 47, embedded in the back of dial 38, andvwi'th which the movable pin 42 is adapted 'to make contact when inserted in any one of a circular series of holes in the face of the dial. A lead 47 from the positive main goes to the dial-operating motor 40, and another lead 48 from this motor leads, along with wires 45 and 46, to a series of automatic stopping, starting and reversing1 switches (not shown), which control the cycle ot operations in the grinding machine. All ot this is shown and described in det-ail in the prior application referred to above. llhen arm 39 is moved to the starting position and connection is established at pin d1,

' termines the grinding time. lWhen the circuit is established at 42, the rotation of the table is stopped, the head 8 is raised, and the door 8 lowered to give access to the glass sheet.

lin addition to the above, mechanism is provided on, and in connection with, the dial 38 for automatically controlling the dow ot abrasive from the several pipes 11, 12 and 13. lmbedded in the dial 38, outside of and concentric with the ring1 a7 are two other contact rings a9 and 50. A pair of contact pins 51 and 52 are adapted to be inserted in any selected one oit a circular series ot holes above the rings d0, 50, respectively, and malte electrical contact with the ring,r underlying the hole. As the control arm 39moves clockwise around the dial 38, contact will be made trom the positive slip-ring 4.4 to the pins 51 and 52 as the arm 30 passes thereover.

lixedly mounted in a portion ot the housing 53| which surrounds the reduction gearing between motor 33 and shaft 29, is a plate or dial 54 centered about the rotary cam-shaft 29. 1n this dial are tixed a plurality of contact pins 55, G, 57 and 58. 'llhese tour pins are all equidistant from the axis ot shaft 29 and are spaced at equal intervals of 90 from one another. Pin 55 is connected to starting pin d1 by wire 59. lPin 55 is connected to ring; 4:9 by `wire 60.

APin 57 is connected to ring'50 by wire 51,

Pin 58 is connected to ring 47 by wire 62. @entered about shaft 29 in dial 54 is a coni tact ring or plate 63. Lead wire 64 connects this ring 53 with one terminal of motor 33. rl`he'other side ot motor 33 is connected by wire G5 to the negative main. Fixed to the end oit shaft 29 is an arm or quadrant titi which carries on its rear tace adjacent the face ot dial 5ft, a 90 contact plate 67 having a central arm v68 adapted to make continuous contact with the ring 63. The

l arcuate contact plate 07 contacts in turn with each of the series of and 58.

1When the Vgrinding machineis idle the cams and 32 extend substantially horizontally in opposite directions from shaft 29,

pins 55, 56, 57

with the cam 31 projecting', upward. At

33 and wire 55 to the negative main.

this time all ot the valves lll, 15 and 15 are Y closed, and no abrasive is permitted to tiow trom the pi eelines to basin 17, and t-hence to the grin ing machine. Contact arc 57, on arm 56, contacts at its forward end with pin 55, and its rear end has just passedlotf vrom pin 58. Now let us assume that the operator has moved the control arm 39 baclr, counter-clockwise, until contact is made with starting pin 41 to start the machine as described above.` A circuit is now completed from the positive main through wire a3, ringr del, control arm 39, pin 41, wire 50, pin 55, arcuate plat/e 67, ring 63, wire 64, motor Motor 33 will now rotate the shaft 20 in a cloclc ,wise direction until plate 67 runs ott' trom sition that it has depressed, and held down,

the shatt 21 which opens valve or orifice 1d. Heavy abrasive may now be forced from pipe-line 11 into the tunnel or basin `17, and thence to the grinding table. The plate 67 is now in contact with pin 56, but no circuit is completed since no contact is had with pin 51 on circular plate 4:0.' The partsremain in this position, and abrasive continues to flow trom pipe-line 11, while the control arm 39 is slowly rotated cloclrwise by motor till contact is made with pin 51., A new circuit is then established as tolu lows :--trom the positive main through wire a3, ring a4, control arm 39, pin 51, ring,n d0, wire 60, pin 55, plate 67, ring 53, wire 5d, motor 33, wire to the negative main. The motor will now rotate shaft 29 and the cams through an arc of 900, until the plate 67 runs oft' from pin 56 and the motor circuit is again broken. During this interval, cam 30 has moved away from the rst pin 21, which has been returned to normal raised position by spring 25, and the flow trom pipe-line 11 is shut od.' At the same time cam 31 has depressed the second shatt 21, valve 15 has-been opened, and the intermediate grade of abrasive may now flow from pipe 12. This continues until control arm 39 is over and contacts with pin 52 when a.

similar circuit is established from pin 52 through ring 50, wire 61, pin 57, and plate 67, to the motor 33 as before. The cam shaft will now be rotated another 90 to shut oit' the dow from pipe 12, and open up valve 16 and allow the finest ,grade of abrasive to flow to the machine. This is the osition of the parts illustrated in the drawings. When the grinding operation has been completed, control arm 89 will contact with stop pin 42, and stopthe machine as above described. At the same' time a circuit is completed through pin 42, ring 17, wire (32, pin 58 and plate 67, to the motor 33 as before. This 'will move the cam 32 away from the operating shaft 2 1, allowing, valve 16 to At a convenient point in each of the close. The blank sector of the cam series, between cams 30 and 32, is now down, and none of the shafts 21 will be depressed. All iow of abrasives is shut oii' andthe machine is idle.

It will be noted that the position of the pins 51 and 52 on dial 38, is adjustable in the same manner as stop pin 42. The length of the clockwise arc'between starting pin 41, and stop pin 42, determine the total grinding period of the machine. The length of arc between pins 41 and 51 determines the portionof this `t-otal grinding time dur# ing which the first orheaviest grade of abrasive will be used. In the same manner the grade is in reservoir 101, the intermediate reservoirs 94 to 100 containing seven interv mediate grades of abrasive, so that the abrasives gradually diminish in size from reserlvoir 93 to reservoir 101. Agitators 102, in each reservoir, keep the abrasives in suspension.

The heavy or coarse abrasive in reservoir -93 is drawn out at 106, by either oneof a pair of parallel pumps 107 or 108, and delivered to the`pipe-line 11'. The alterna tive pumps 107 and 108 are to allow for re lpairs to either without shutting down the system. When desired, to vary the grade of abrasive used, reservoirs 94 and 95 may be drawn from in addition to reservoir 93. By an exactly similar system of pumps, reservoirs 96, 97 and 98, supply the lnte'rmediate pipe-line 12, and the lightest abrasive is supplied to pipe-line 13 in like manner from reservoirs 99, 100 and 101. The pipe-lines 11, 12 and 13, after passing by all of the grinding units, loop back and discharge into the reservoirs 93, 96 and 99, respectively.

1 elines, near its discharge end, is located apciitof valve ,109, preferably of the gate type, as shown in Figs. 9 and 10. The operating stem 110 of each valve, has a roller 111 traveling in the cam slot 112 ofa large rotary cam 113, mounted on a horizontal shaft .114. As shown in Fig. 10, the three cams may all be conveniently mounted on the same drive shaft .114, which is driven through. suitable reductionA gearing 115 from a motor 116 continuously running in the normal operation of the system. When pin 111 is in the outer portion 117 of the cam-slot, the valve is closed, and when the pin is in the inner arc 118 of the slot the .valve is open.

manana These gate-valves109 will be intermittently opened and closed by the mechanism just described. I will describe the operation of the hea-vier abrasive in pipe-line 1], although an exactly similar cycle of events is simultaneously but independently taking place in the pipe-lines 12 and 13. Since the pump 107 or 108 is constantly operating, a pressure is being put upon the abrasive mixture in the pipe-line tending to cause a flow therethrough. When valve 109 is open, this How may proceed through the loop and back to the reservoir 93, although some of it may run through such of the valves 14 as are then open. lVhen valve 109 is closed, the How through the pipe or conduit back to the reservoir is entirely cut off and the only outlet for the abrasive, now under considerable pressure from the pump, is through the open valves 14. In this way a positive flow of abrasive through all of the valves 14 then open is insured, and there will be sulicient force behind this flow to blow out any valve that may tend to become plugged by an accumulation of abrasive. The intermittent fiow through the pipe-line, in the intervals when the valves 109 are open, will serve to keep the abrasive in suspension in the pipe. Such abrasive as passes by the valve 109 during these intervals, is forced back into the reservoir 93 and used again. As stated above, the same cycle of operations is independently taking place in the other pipe-lines 12 and 13.

The reservoirs 93 to 101 may be supplied with additional abrasive when necessary in any suitable manner, but it is preferable that a system be used whereby the partially used abrasive thrown -from the grinding machines is collected, regraded, and returned to the reservoirs, new sand and abrasive being addedvonly when necessary. There are many ways in which this may be done, but the following described system is simple and well adapted for the purpose.

The abrasive mixtures fed to the grinding tables as above described, as well as the water used in washing the tables and sheets, iows into the drain pipes 10, from which it drains eventually into the sump 69. An

agitator may be used in this sump to keep' the abrasive materials in suspension.

By means of a pump 71, driven by motor 72, this mixture is elevated from the sump, through pipe73, to a distributing trough 74, from which it is discharged at will through valved outlets 75, 7 G or 77 to any one or all of a plurality of series of grading tanks 78, 79 and 80.' The three series of grading tanks here shown are duplicates of one another and a description of one will answer for all. It is to be understood, that one series o" tanks may be sufficient, and the duplication is merely to provide a greater capacity, or to allow for one grading series being temporarily out of commission without requiring the cessation of operations.

Each grading system comprises a longitudinal series of separate tanks here numbered from 81 to 90, respectively. The abrasive mixture is first delivered 'from trough 74 into tank 81. The division walls between the several tanks of the series are successively lower from tank 81 to tank 90, so that the mixture will successively overflow from one tank to the next. As shown more clearly in F ig. 5, the overflow` from .tank 81, passes over partition wall 91 into tank 82, thence over wall 92 to tank 83, and so on throughout the series.. While the liquid mixture remains in each successive tank, the then remaining heavier portions of the abrasives will settle to the bottom of the tank, and it will be obvious that the deposit collected in each tank will be successively lighteras the flow continues throughout the tanks from 81 to 90.

The heaviest or coarsest abrasive is collected in the tanks V8 1, and is delivered as needed from these tanks to the reservoir ,93.

lin the same manner the collection from vtanks 82 to 89 is delivered to reservoirs 94 to 101, respectively. Of course, it is to be understood that valves such as 103 are provided in each of the pipes connecting the tanks with the reservoirs to shut off or turn on the How as may be desired. In this connection it may be stated that numerous valves may be used wherever considered necessary in the pipe systems, and no description of each valve will be here attempted. Many are indicated in the drawings which will not be described.

The lighter substances, 'such as ground glass, collected in the last tanks 90, flew away through pipes 104 to the sewer. The

water overflowing from tanks 90 passes back through pipe 105 to the sump. Any overflow from the several reservoirs may also be discharged into this pipe 105. 1

New, unused abrasives may beadded when necessary to the reservoirs, to the grading tanks 81 or to the sump 69, in any suitable` A system quite similar to the labove may in each conduit for forcing the abrasive` therethrough, and means adjacent each ma chine for selectively feeding abrasive to the machine from the conduits.

2. An apparatus for supplying abrasives to a plurality of sheet-surfacing machines, comprising a plurality of reservoirs for different grades of abrasive, a conduit from each reservoir extending past the several machines, and back to the reservoir, a pump in each conduit circuit for forcing abrasive therethrough, and means adjacent each machine for feeding abrasive 'to the machine from the conduits.

3. An apparatus for supplying abrasives to a plurality of sheet-.surfacing machines, comprising a plurality of reservoirs for different grades of abrasive, a pipe circuit from each reservoir, extending past the' several machines, and back to the reservoir, means in each circuit for forcing abrasive therethrough, a valve in each pipe adjacent each machine, and means for selectively operating the valves to permit the desired abrasive to be delivered to the machine.

4c. An apparatus for supplying abrasives to a plurality of sheet-surfacing machines, comprising a plurality of reservoirs for different grades of abrasive,l a pipe circuit 'fromeach reservoir extending past the several machines, and back to the reservoir, means 1n each circuit for forcing abrasive therethrough, a valve 1n each pipe adjacent each machine, and means for automatically for permitting abrasive to be delivered to the machine from the conduits, a sump into which the abrasives flow from the several machines, a series of grading tanks, a pump to feedthe abrasive mixture from the sump to the' grading tanks, and means for directing the graded abrasives from the tanks to the reservoirs..

6. In combination with a sheet-surfacing machine, a series of conduits adjacent the machine through each of which a flow of abrasive may be enforced, a valve in each conduit, a cam shaft for operating the valves, a motor to turn the shaft, a rotary switch operated from the cam shaft to stop the motor after the desired movement has been given the shaft, and timing means to start the motor at desired intervals.

7. An apparatus for supplying abrasive to a sheet-surfacing machine, comprising a container for the' abrasive supply consisting of a reservoir and a conduit leading from. the reservoir past the machine and back to the reservoir, means for permitting abrasive to be fed from the conduit to the machine, means for maintaining a continuous pressure on the abrasive in the conduit,I and means for alternately directing this pressure to force portions of the abrasive to the machine, or to force a circulation of abrasive through the conduit.

8. An apparatus for supplying abrasive to a sheet-surfacing machine, comprising a container for the abrasive supply, consisting of a reservoir and a conduit leading -trom the reservoir ast the machine and back to the reservoir, intermediate means operable to permit abrasive to be fed from the conduit to the machine, means `for maintaining a continuouspressure on the abrasive in the conduit, and a valve in the conduit for `intermittently closing communication between the discharge end of theconduit and the reservoir'.

9. An apparatus for supplying abrasives ,to a sheet-surfacing machine, comprising a plurality of containers .for the several grades of abrasive mixtures, each container consisting o'a reservoir and a 'conduit'leading from the reservoir past the machine and back to the reservoir, means operable selectively for opening communication from the several conduits to the machine, means for maintaining a continuous pressure on the abrasive in each conduit, and means operable for .alternately directing this pressure to force portions of the selected grade of abrasive to the machine, or to force acirculation of abrasive through the conduit.

10. An apparatus for supplying abrasives to a sheet-surfacing machine, comprising a pluralityvof containers for the several grades of abrasive mixtures, each container consisting of a reservoir and a conduit leading from the reservoir past the machine and back to the reservoir, means for predeterminedly selectively 4automaticallv at ltimed intervals opening communication from 'from the reservoir past the machine and back to the reservoir, means operable selectively for opening communication from the several conduits to the machine, means for maintaining a continuous pressure on the abrasivey in each conduit, and a valve in each conduit 'for intermittently closing commenace munication between the discharge end ci the conduit and. the reservoir.

l2. An apparatus for supplying abrasive to plurality of sheet-surfacing machines, comprising a container for the abrasive mixture extending adjacent all of the machines, means operable selectively for opening communication :from the container to each oit4 the machines, means for maintaining a continuous pressure on the abrasive supply in 'the container, and means operable or alternately directing this pressure to force portions o the abrasive to the selected machines or to maintain the abrasive supply in suspension in the container.-

13. An apparatus for supplying abrasive to .a plurality of sheet-surfacing machines, comprising a container for the abrasive mixture consisting of a reservoir and a conduit extending from the reservoir past all of the machines and back to the reservoir, means operable selectively for opening communication from the conduit to each of the machines, means for maintaining a continuous pressure on the abrasive in the conduit, and means operable for alternately directing this pressure to `force a flow of abrasive to the selected machines, or to force a circulation of abrasive -through the conduit.

M. An apparatus for supplying abrasive to a plurality of sheet-surfacing machines, comprising a container for the abrasive mixture consisting of a reservoir and a conduit extending from the reservoir past all of the machines and back to the reservoir, means operable 'selectively for opening communication from the conduit to each ci' the machines, means for maintaining 'a continuous pressure on the abrasive in the conduit, and an intermittently operating'valve in cach conduit for opening and closing'communication' between the discharge end of the conduit and the reservoir.

. '15. An apparatus for sup lying abrasivos to a plurality of sheet-sur :icing machines, comprising a plurality of containers for 'the several grades of abrasive mixtures, each container comprising a reservoir and a conduit extending from the reservoir past all of the machines and back to Ythe reservoir,

means operable selectively for opening communicatlon from any of the several conduits to any ofthe several machines, means for maintaining a continuous pressure on the abrasive in each conduit, and means operable for alternately directing this pressure 'to force portions of the abrasive to the selected machines, 'or to force a circulation of the abrasiveI mixture through the conduit.,

16. An apparatus for supplying abrasives to a plurality of sheet-surfacing machines, comprising a plurality of containers for the several grades of abrasive mixtures, each container comprising a reservoir and a, conduit extending from the reservoir past all of i matically .alternately directing this pressure the machines and back to the reservoir, means for predeterminedly selectively automatically at timed intervals opening communication from any of the several conduits to any of the several machines, means for maintaining a continuous pressure on the abrasive in each conduit, and means for autoto force portions of the abrasive to the selected machines, or to force a circulation of the abrasive mixture through the conduit.

17. An apparatus for supplying abrasives to a plurality of shcet-surfacing machines, comprising a plurality of containers for the several grades of abrasive mixtures, each container comprising a reservoir'a'nd a conduit extending from the reservoir past all of the machines and back to the reservoir, means operable selectively for opening communication from any of the several conduits to any of the several machines, means for maintaining a continuous pressure on the abrasive in each conduit, and a valve in each conduit for intermittently closing communication between the discharge end of the conduit and the reservoir.

18. ln an apparatus for feeding abrasives, a container for the abrasive comprising a reservoir and a conduit both ends of which terminates in the reservoir, outlets in the conduit for feeding abrasive therefrom, a pump in the conduit adjacent one terminal lthereof for forcing abrasive from the reservoir into the conduit, and a valve adjacent `the. other terminal of the conduit `operable for intermittently closing communication' between the conduit and the reservoir.\

i9. ln an apparatus for feeding abrasives,

la container for the abrasive comprising a 20. An abrasive grading and supplying apparatus for use in connection with sheet surfacing machines, comprising a grader, a reservoir for abrasive, means connecting said grader to said reservoir, a conduit from the reservoir extending past the several` machines, and, back to the reservoir, a return conduit connecting the machines to the grader, means forl forcing the abrasive through the reservoir conduit, means adjacent each machine for feeding the abrasive to the machine from this conduit and means for forcing the used abrasive from the machine to the grader.

21.'In combinationl with a surfacing machine, a system of abrasive supply comprising a reservoir of abrasive mixture, a supply circuit, means for maintaining a. constant pressure Within said circuit and means operable to release the abrasive under said pressure to said machine or to maintain a flow thereof throughout the circuit exclusive of the surfacing machine.

22. Inv combination with' a surfacing machine, a system of abrasive supply'comprising reservoirs of abrasive mixture, supply circuits for separate grades of abrasives, means for maintaining a constant pressure Within said circuits and means operable to release' each gradeof abrasive under said pressure to said machine or to maintain a iiovv thereof throughout its circuit exclusive of the surfacing machine.

23. In combination with a plurality of surfacing machines, a system of`ab-rasive supply comprising a reservoir of abrasive mixture, a supply circuit extending past the several machines, means for maintainin a constantpressure Within said circuit .an means operable to release the abrasive under said pressure to any of said machines or to maintain a flow thereof throughout the cir cuit exclusive of said surfacing machines.

24. In combination with a plurality of surfacing machines, a system of abrasive supply comprising reservoirs for' several grades of abrasive mixtures, supply circuits for the separate grades of abrasives extending past `the several machines, means for maintaining a constant pressure Within said circuits and means operable to selectively release the abrasive under said pressure to any of said machines or to maintain a dow thereof throughout said circuits exclusive of said surfacing machines. i

Signed at Toledo, in the county of Lucas, and State of Ohio', this 25th day of August,

JOSEPH P. CROWLEY. 

